1. Field of the Invention
The present invention relates to a semiconductor device suitably applicable to a user terminal such as a portable telephone and a method of manufacturing the same as well as a communication method suitable for utilizing the semiconductor device.
2. Description of the Background Art
It is said that illegal use of a user terminal such as a portable telephone, i.e., a criminal act of pretending that one""s user terminal belongs to another person in a communication network by changing the identification number or the like to evade paying the communication charges is recently on the increase. While such illegal use must be socially controlled through legal action similarly to other crimes as a matter of course, it is recognized as one of particularly important countermeasures for preventing such a crime to make illegal use technically difficult, i.e., to improve a technical barrier (security) against the illegal use.
FIG. 93 is an explanatory diagram quoted from a report in xe2x80x9cNikkei Electronicsxe2x80x9d No. 736 dated Feb. 8, 1999, pp. 155 to 162 (hereinafter referred to as literature 1), showing an exemplary countermeasure against illegal use currently carried out in relation to a portable telephone. As described in literature 1, the method shown in FIG. 93 is regarded as providing the highest security among the current countermeasures against illegal use, and utilizes a procedure of xe2x80x9cauthenticationxe2x80x9d.
In this method, each portable telephone 903 is provided with a serial number (ESN: Electronic Serial Number) for the portable telephone 903, shared secrete data (SSD) shared by the portable telephone 903 and an authentication center 901 of a communications common carrier and a mobile identification number (MIN). The identification number is encoded to a cipher referred to as AUTHREQ on the basis of a CAVE (Cellular Authentication and Voice Encryption) algorithm 904. In this encryption, a random number referred to as RAND output from a mobile exchange center 902 of the communications common carrier is employed.
The communications common carrier decodes the cipher AUTHREQ transmitted from the portable telephone 903 on the basis of the CAVE algorithm 905. The decoded identification number is compared with an identification number including the shared secret data SSD held only by the authentication center 901 so that a determination on authorization or unauthorization of communication is made in response to the result of the comparison. Thus, whether or not the user of the portable telephone 903 is legal is checked, i.e., authenticated on the basis of the shared secret data SSD shared only by the portable telephone 903 and the communications common carrier.
Also for the authentication system shown in FIG. 93 regarded as the strongest countermeasure against illegal use at present, however, it is said that illegal use is now spreading while avoiding the authentication. It is said that the main technical factor resides in that the identification number supplied to the portable telephone 903 is written in a reloadable flash memory (flash ROM), as described in literature 1.
FIG. 94 is a block diagram briefly showing the internal structure of a conventional portable telephone 903. The conventional portable telephone 903 comprises a communication circuit 907 and a flash memory 908. The communication circuit 907 operates in accordance with a program written in the flash memory 908. The flash memory 908 also holds an identification ID, and the communication circuit 907 performs encoding on the basis of the identification number ID read from the flash memory 908 for transmitting a cipher AUTHREQ generated by encoding to the communications common carrier.
The reloadable flash memory 908 is employed as a storage medium since it is necessary to cope with program change by the communications common carrier such as change to a program corresponding to a new communication system, for example. If an unreloadable mask ROM is employed, it is impossible to cope with program change, and the identification number must be recorded with a mask pattern responsive to the identification number varying with each individual in the process of manufacturing the mask ROM, to result in reduction in the manufacturing efficiency and increase in the manufacturing cost.
According to a first aspect of the present invention, a semiconductor device comprises a semiconductor element having a polycrystal and an encoder circuit converting an electric characteristic of the semiconductor element to a digital signal so that the value is dispersed in derivation from dispersion of the crystal structure of the polycrystal thereby generating and outputting a code.
According to the first aspect, the value of the code is dispersed among individuals, whereby the code can be utilized as an identification code for a system or the like assembled with the device of the present invention. Further, the code is generated by utilizing dispersion of crystal structures of polycrystals manufactured through the same step among the individuals, whereby manufacturing of the device is simplified. In addition, the characteristic of the semiconductor element forming the basis of the code cannot be externally changed and hence the semiconductor device implements a high barrier against illegal change of the code.
According to a second aspect of the present invention, the semiconductor device further comprises a comparator circuit regarding the code output from the encoder circuit as a first code, comparing an externally input second code with the first code, determining agreement or approximation between the codes and outputting a prescribed signal indicating the result of determination.
According to the second aspect, the comparator circuit determines agreement or approximation between the codes, whereby the codes can be utilized for authentication.
According to a third aspect of the present invention, the semiconductor device further comprises a prescribed circuit including a circuit part selectively entering an operating or non-operating state in response to the prescribed signal.
According to the third aspect, the semiconductor device comprises the prescribed circuit including the circuit part selectively entering an operating or non-operating state on the basis of the determination of the comparator circuit, whereby a prescribed operation of a system can be authorized and unauthorized in response to the result of determination of a password or authentication of the code by forming part of a circuit implementing functions of the system by the prescribed circuit and utilizing the code as the password or a code for authentication.
According to a fourth aspect of the present invention, the semiconductor element and the encoder circuit are formed on a single semiconductor substrate.
According to the fourth aspect, the semiconductor element and the encoder circuit are formed on the single semiconductor substrate, whereby not only characteristic data of the semiconductor element is unchangeable but also output of the encoder circuit can be prevented from being changed by external input of a signal in the encoder and hence the barrier against illegal use of the system assembled with the inventive device is further improved.
According to a fifth aspect of the present invention, the encoder circuit includes a conversion circuit converting an electric characteristic of the semiconductor element to a digital signal so that the value is dispersed in derivation from dispersion of the crystal structure of the polycrystal thereby generating a code, and a code memory formed on the single semiconductor substrate for storing the code generated by the conversion circuit in a nonvolatile manner and reading the code thereby outputting the same as the code output from the encoder circuit.
According to the fifth aspect, the semiconductor device comprises the code memory, whereby the code does not fluctuate even if the temperature or the power supply voltage fluctuates but a constant code is stably obtained indefinitely. The code memory is formed on the semiconductor substrate in common with the semiconductor element and the encoder circuit, and hence the code stored in the code memory cannot be illegally rewritten from outside.
According to a sixth aspect of the present invention, the semiconductor device further comprises a comparator circuit formed on the single semiconductor substrate for regarding the code output from the encoder circuit as a first code, comparing an externally input second code with the first code, determining agreement or approximation between the codes and outputting a prescribed signal indicating the result of determination.
According to the sixth aspect, the comparator circuit is also formed on the single semiconductor substrate, whereby a code to be input in the comparator circuit cannot be illegally changed from outside. Thus, the barrier against illegal use is further improved.
According to a seventh aspect of the present invention, the semiconductor device further comprises a prescribed circuit, formed on the single semiconductor substrate, including a circuit part selectively entering an operating or non-operating state in response to the prescribed signal.
According to the seventh aspect, the prescribed circuit is also formed on the single semiconductor substrate, whereby the prescribed signal cannot be externally input. Thus, the barrier against illegal use is further improved.
According to an eighth aspect of the present invention, the semiconductor element includes a MOS transistor, at least a channel region of the MOS transistor is made of a polycrystalline semiconductor serving as the polycrystal, and the channel width and the channel length of the MOS transistor are set in the range of 0.5 to 10 times the mean crystal grain size of the polycrystalline semiconductor.
According to the eighth aspect, the channel width and the channel length of the MOS transistor are optimized with respect to the crystal grain size, whereby dispersion of the code between individuals can be increased.
According to a ninth aspect of the present invention, the semiconductor element includes a MOS transistor, at least a channel region of said MOS transistor is made of a polycrystalline semiconductor serving as the polycrystal, and the comparator circuit includes a sweep circuit sweeping a gate voltage of the MOS transistor, an approximation level calculation circuit calculating an approximation level between the first code output from the encoder circuit and the second code in the process of sweeping the gate voltage, and an evaluation circuit determining whether or not the approximation level calculated by the approximation calculation level circuit exceeds a reference value and outputting a signal indicating the result of determination as the prescribed signal.
According to the ninth aspect, whether or not the approximation level exceeds the reference value is determined in the process of sweeping the gate voltage, whereby approximation and agreement of the codes can be correctly determined while eliminating influence by fluctuation of the temperature and the power supply voltage.
According to a tenth aspect of the present invention, the reference value can be set from outside the semiconductor device.
According to the tenth aspect, the reference value for the determination can be externally set and hence the determination can be made at a proper level in response to difference of importance of authentication or the like.
According to an eleventh aspect of the present invention, the comparator circuit includes a measuring circuit measuring the electric characteristic of the semiconductor element and outputting the measured value as a digital signal, a data memory storing the digital signal, a code supervisory circuit determining whether or not the first code suffers fluctuation on the basis of the digital signal output from the measuring circuit and the digital signal stored in the data memory and updating the digital signal stored in the data memory with the digital signal obtained by new measurement, a code correction circuit outputting the first code while correcting the value of the first code when the code supervisory circuit detects the fluctuation or without correcting the value when no fluctuation is detected, and a determination circuit comparing the code output from the code correction circuit with the second code, determining agreement or approximation between the codes and outputting a signal indicating the result of determination as the prescribed signal.
According to the eleventh aspect, fluctuation of the code is automatically corrected, whereby stable determination can be maintained by canceling influence by fluctuation of the electric characteristic of the semiconductor element derived from xe2x88x92BT stress.
According to a twelfth aspect of the present invention, the code supervisory circuit determines presence/absence of the fluctuation and updates the digital signal stored in the data memory with the digital signal obtained by new measurement only when every digital signal obtained by the measuring circuit through a prescribed number of a plurality of times of measurement is different from the digital signal stored in the data memory.
According to the twelfth aspect, fluctuation of the code is determined only when change of the characteristic is recognized over a plurality of times in measurement of the electric characteristic of the semiconductor element, whereby false determination can be suppressed.
According to a thirteenth aspect of the present invention, the semiconductor element includes a first polycrystalline thin-film transistor, and the semiconductor device further comprises a static RAM, formed on the single semiconductor substrate, having a second polycrystalline thin-film transistor in a memory cell.
According to the thirteenth aspect, the semiconductor element and the encoder circuit are integrated into the SRAM utilized for an extensive system, whereby a function of identification can be added to the extensive system. Further, the SRAM includes the polycrystalline thin-film transistor, whereby the number of manufacturing steps required for adding a new polycrystalline thin-film transistor for identification and the cost therefor can be saved.
According to a fourteenth aspect of the present invention, the semiconductor device further comprises a CDMA (code division multiple access) code generation circuit generating a CDMA code on the basis of the code output from the encoder circuit, a modulation circuit modulating a transmitted signal on the basis of the CDMA code, and a demodulation circuit demodulating a received signal on the basis of the CDMA code.
According to the fourteenth aspect, codes having low correlation are employed for generating the CDMA code, whereby a communication system having a low crosstalk level similarly to a conventionally known communication system using the CDMA system can be implemented at a low cost.
According to a fifteenth aspect of the present invention, the prescribed circuit is a communication circuit transmitting and receiving a signal to and from an external device, and receiving the second code and transmitting the same to the comparator circuit.
According to the fifteenth aspect, the prescribed circuit is the communication circuit receiving and transmitting the second code to the comparator circuit, whereby the semiconductor device is suitable for application to a communication terminal employing the code for authentication.
According to a sixteenth aspect of the present invention, the semiconductor device further comprises a temperature sensor measuring the temperature of the semiconductor element, and a voltage sensor measuring a power supply voltage applied to the semiconductor element, while the communication circuit transmits temperature data obtained by the temperature sensor through measurement and voltage data obtained by the voltage sensor through measurement.
According to the sixteenth aspect, the communication circuit transmits the temperature data and the voltage data, whereby the semiconductor device is suitable for application to a communication terminal implementing stable authentication while canceling influence by the temperature and the voltage or influence by xe2x88x92BT stress.
According to a seventeenth aspect of the present invention, the semiconductor device further comprises an error operation circuit comparing the electric characteristic of the semiconductor element with characteristic data and calculating an error thereof and an error memory storing the error, and the communication circuit receives the characteristic data and transmitting the same to the error operation circuit while reading and transmitting the error stored in the error memory.
According to the seventeenth aspect, the error is calculated and stored while the stored error is read and transmitted, whereby the semiconductor device is suitable for application to a communication terminal implementing stable authentication while canceling influence by xe2x88x92BT stress.
According to an eighteenth aspect of the present invention, a semiconductor device comprises M (xe2x89xa72) by N (xe2x89xa71) MOS transistors arranged in the form of a matrix of M rows and N columns, having at least channel regions of said M by N MOS transistors being made of a polycrystalline semiconductor, a power supply line connected to either source electrodes or drain electrodes of the M by N MOS transistors, M bit lines respectively corresponding to said M rows, each one of said M bit lines being connected in common to the other ones of the source electrodes or the drain electrodes of the N MOS transistors belonging to corresponding one of said M rows, and N word lines respectively corresponding to said N columns, each one of said N word lines being connected in common to gate electrodes of the M transistors belonging to corresponding one of said N columns.
According to the eighteenth aspect, the semiconductor device comprises the plurality of MOS transistors connected to be individually specifiable with the word lines and the bit lines and at least channel regions of the MOS transistors are made of a polycrystalline semiconductor, whereby codes of a plurality of bits dispersed among devices can be readily generated.
According to a nineteenth aspect of the present invention, a semiconductor device comprises M (xe2x89xa72) by N (xe2x89xa71) resistive elements arranged in the form of a matrix of M rows and N columns, having resistors made of a polycrystalline semiconductor, M bit lines respectively corresponding to said M rows, each one of said M bit lines being connected in common to first ends of the N resistive elements belonging to corresponding one of said M rows, and N word lines respectively corresponding to said N columns, each one of said N word lines being connected in common to second ends of the M resistive elements belonging to corresponding one of said N columns.
According to the nineteenth aspect, the semiconductor device comprises the plurality of resistive elements connected to be individually specifiable with the word lines and the bit lines and having the resistors made of a polycrystalline semiconductor, whereby codes of a plurality of bits dispersed among devices can be readily generated.
The present invention is also directed to a method of manufacturing a semiconductor device. According to a twentieth aspect of the present invention, a method of manufacturing a semiconductor device comprises steps of (a) depositing an amorphous semiconductor layer on an insulator layer by executing chemical vapor deposition with reactive gas at a first temperature, and (b) converting the amorphous semiconductor layer to a polycrystalline semiconductor layer by performing annealing at a second temperature over a prescribed time, while the type of the reactive gas, the first temperature, the second temperature and the prescribed time are so set that the mean crystal grain size of the polycrystalline semiconductor layer is at least 0.1 xcexcm.
According to the twentieth aspect, the polycrystalline semiconductor layer is so formed that the mean crystal grain size is at least 0.1 xcexcm, whereby an element having large dispersion of the electric characteristic can be readily formed with the polycrystalline semiconductor layer.
According to a twenty-first aspect of the present invention, a method of manufacturing a semiconductor device comprises steps of (a) forming an impurity layer on a main surface of a semiconductor substrate by selectively introducing an impurity, (b) forming an insulator layer on the main surface of the semiconductor substrate, (c) depositing a polycrystalline semiconductor layer on the insulator layer, (d) separating the polycrystalline semiconductor layer into a first semiconductor layer and a second semiconductor layer by performing patterning so that the second semiconductor layer covers the impurity layer, (e) selectively forming a channel region, a source region and a drain region of a MOS transistor having the first semiconductor layer as a gate electrode in the main surface of the semiconductor substrate, and (f) selectively forming a channel region opposed to the impurity layer as well as a source region and a drain region holding the channel region therebetween by selectively introducing an impurity into the second semiconductor layer.
According to the twenty-first aspect, the gate electrode of the bulk MOS transistor and the semiconductor layer of the thin-film MOS transistor are formed by patterning the common polycrystalline semiconductor layer, whereby a semiconductor device having two types of MOS transistors formed on a common semiconductor substrate can be manufactured through a small number of steps at a low cost.
According to a twenty-second aspect of the present invention, a method of manufacturing a semiconductor device comprises steps of (a) forming an insulator layer on a main surface of a semiconductor substrate, (b) depositing a polycrystalline semiconductor layer on the insulator layer, (c) separating the polycrystalline semiconductor layer into a first semiconductor layer and a second semiconductor layer by patterning, (d) selectively forming a channel region, a source region and a drain region of a MOS transistor having the first semiconductor layer as a gate electrode in the main surface of the semiconductor substrate, and (e) forming a resistor and an electrode holding the same by selectively introducing an impurity into the second semiconductor layer.
According to the twenty-second aspect, the gate electrode of the bulk MOS transistor and a thin-film resistive element are formed by patterning the common polycrystalline semiconductor layer, whereby a semiconductor device having two types of elements formed on a common semiconductor substrate can be manufactured through a small number of steps at a low cost.
According to a twenty-third aspect of the present invention, a method of manufacturing a semiconductor device comprises steps of (a) selectively implanting a main component element of a semiconductor substrate into a main surface of the semiconductor substrate thereby selectively converting the main surface to an amorphous state, (b) converting the portion converted to the amorphous state to a polycrystalline state by annealing, and (c) forming a single-crystalline semiconductor element and a polycrystalline semiconductor element into the semiconductor substrate by selectively forming impurity regions both in a portion of the semiconductor substrate converted to the polycrystalline state and in a remaining portion.
According to the twenty-third aspect, the portion converted to a polycrystalline state is selectively formed on the main surface of the semiconductor substrate through implantation of the element and annealing so that elements are formed respectively, whereby a semiconductor device having a single-crystalline semiconductor element and a polycrystalline semiconductor element of a bulk type on a common semiconductor substrate is obtained.
According to a twenty-fourth aspect of the present invention, a method of manufacturing a semiconductor device comprises steps of (a) forming an insulator layer on a main surface of a semiconductor substrate, (b) depositing a first polycrystalline semiconductor layer on the insulator layer, (c) separating the first polycrystalline semiconductor layer into a first electrode and a second electrode by patterning, (d) forming a first insulator film and a second insulator film to cover the first electrode and the second electrode respectively, (e) depositing a second polycrystalline semiconductor layer to cover the insulator layer and the insulator films, (f) separating the second polycrystalline semiconductor layer into a third electrode on the insulator layer, a fourth electrode covering the first insulator film and a third polycrystalline semiconductor layer covering the second insulator layer by patterning, (g) selectively forming a channel region, a source region and a drain region of a MOS transistor having the third electrode as a gate electrode in the main surface of the semiconductor substrate, and (h) selectively forming a channel region, a source region and a drain region of a MOS transistor having the second electrode as a gate electrode in the third polycrystalline semiconductor layer by selectively introducing an impurity into the third polycrystalline semiconductor layer.
According to the twenty-fourth aspect, an electrode of a capacitive element and the gate electrode of the thin-film MOS transistor are formed while the gate electrode of the bulk MOS transistor, another electrode of the capacitive element and the semiconductor layer of the thin-film MOS transistor are formed by patterning the common first and second polycrystalline semiconductor layers, whereby a semiconductor device having three types of elements formed on a common semiconductor substrate can be manufactured through a small number of steps at a low cost.
The present invention is also directed to a communication method. According to a twenty-fifth aspect of the present invention, a communication method comprises the steps of (a) communications common carrier equipment storing a code identical to the first code of the semiconductor device according to any of the fifteenth to seventeenth aspects, and (b) the communications common carrier equipment and a communication terminal which has the semiconductor device, making communication with each other after the step (a), while the step (b) includes the steps of (b-1) the communications common carrier equipment transmitting the stored code to the communication terminal as the second code, (b-2) the communication terminal receiving the transmitted second code in the communication circuit, (b-3) the comparator circuit determining the agreement or approximation on the basis of the received second code, and (b-4) the communication circuit stopping communication when neither agreement nor approximation is confirmed in the determination.
According to the twenty-fifth aspect, the communication terminal is authenticated with a code randomized by dispersion of the crystal structure of the polycrystal, whereby a barrier against illegal use can be improved at a low cost.
According to a twenty-sixth aspect of the present invention, a communication method comprises the steps of (a) communications common carrier equipment for storing the first code or the electric characteristic of the semiconductor device according to the sixteenth aspect as a function of temperature of the semiconductor element and power supply voltage for the semiconductor element, and (b) the communications common carrier equipment and a communication terminal which has the semiconductor device, making communication with each other after the step (a), while the step (b) includes the steps of (b-1) the communication terminal transmitting the temperature data and the voltage data, (b-2) the communications common carrier equipment receiving the temperature data and the voltage data, (b-3) the communications common carrier equipment calculating a code under conditions expressed by the temperature data and the voltage data on the basis of the first code or the electric characteristic as the stored function, (b-4) the communications common carrier equipment transmitting the calculated code to the communication terminal as the second code, (b-5) the communication terminal receiving the transmitted second code in the communication circuit, (b-6) the comparator circuit determining the agreement or approximation on the basis of the received second code, and (b-7) the communication circuit stopping communication when neither agreement nor approximation is confirmed in the determination.
According to the twenty-sixth aspect, the codes are generated on the basis of the temperature data and the voltage data so that authentication is performed on the basis thereof, whereby stable authentication can be performed while suppressing influence by fluctuation of the temperature and the power supply voltage.
According to a twenty-seventh aspect of the present invention, a communication method comprises the steps of (a) communications common carrier equipment storing the electric characteristic of the semiconductor device according to the sixteenth aspect as a function of temperature of the semiconductor element and power supply voltage for the semiconductor element, and (b) the communications common carrier equipment and a communication terminal which has the semiconductor device, making communication with each other after the step (a), while the step (b) includes the steps of (b-1) the communication terminal transmitting the temperature data and the voltage data, (b-2) the communications common carrier equipment receiving and storing the temperature data and the voltage data, (b-3) the communications common carrier equipment predicting a shift quantity of the electric characteristic derived from xe2x88x92BT stress on the basis of the electric characteristic as the stored function and previously received temperature data and voltage data, (b-4) calculating a code under conditions expressed by the temperature data and the voltage data received in said step (b-2) in consideration of the shift quantity on the basis of the predicted shift quantity and the temperature data and the voltage data received in the step (b-2), (b-5) the communications common carrier equipment transmitting the calculated code to the communication terminal as the second code, (b-6) the communication terminal receiving the transmitted second code in the communication circuit, (b-7) the comparator circuit determining the agreement or approximation on the basis of the received second code, and (b-8) the communication circuit stopping communication when neither agreement nor approximation is confirmed in the determination.
According to the twenty-seventh aspect, the code is calculated on the basis of previous communication history as well as present temperature data and voltage data and authentication is performed on the basis thereof, whereby stable authentication can be performed while suppressing influence by xe2x88x92BT stress in addition to influence by the temperature and the power supply voltage.
According to a twenty-eighth aspect of the present invention, a communication method comprises the steps of (a) communications common carrier equipment storing the electric characteristic of the semiconductor device according to the seventeenth aspect as a function of temperature of the semiconductor element and power supply voltage for the semiconductor element, and (b) the communications common carrier equipment and a communication terminal which has the semiconductor device, making communication with each other after the step (a), while the step (b) includes the steps of (b-1) the communication terminal transmitting the temperature data, the voltage data and the error in precedent communication, (b-2) the communications common carrier equipment receiving the transmitted temperature data, voltage data and error, (b-3) the communications common carrier equipment calculating the electric characteristic under conditions expressed by the temperature data and the voltage data received in said step(b-2) in consideration of a shift quantity derived from xe2x88x92BT stress on the basis of the electric characteristic as the stored function and the temperature data, the voltage data and the error received in the step (b-2), (b-4) the communications common carrier equipment converting the calculated electric characteristic to a code, (b-5) the communications common carrier equipment transmitting the calculated code to the communication terminal as the second code while transmitting the calculated electric characteristic to the communication terminal as the characteristic data, (b-6) the communication terminal receiving the transmitted second code and the characteristic data in the communication circuit, (b-7) the error operation circuit calculating the error on the basis of the received characteristic data, (b-8) the error memory storing the calculated error, (b-9) the comparator circuit determining the agreement or approximation on the basis of the received second code, and (b-10) communication circuit stopping communication when neither agreement nor approximation is confirmed in the determination.
According to the twenty-eighth aspect, the code is calculated on the basis of the error, the temperature data and the voltage data and authentication is performed on the basis thereof, whereby stable authentication can be performed while suppressing influence by xe2x88x92BT stress in addition to influence by the temperature and the power supply voltage.
According to a twenty-ninth aspect of the present invention, a communication method comprises the steps of (a) communications common carrier equipment storing a code identical to the code output from the encoder circuit of the semiconductor device according to the fourteenth aspect, and (b) the communications common carrier equipment and a communication terminal which has the semiconductor device, making communication with each other after the step (a), while the communication step (b) includes the steps of (b-1) the communication terminal generating the CDMA code on the basis of the code generated by the encoder circuit and modulating a transmitted signal while demodulating a received signal on the basis of the generated CDMA code, and (b-2) the communications common carrier equipment generating a CDMA code identical to the CDMA code of the step (b-1) on the basis of the stored code and modulating a transmitted signal while demodulating a received signal on the basis of the generated CDMA code.
According to the twenty-ninth aspect, codes having low correlation are employed for generating the CDMA code, whereby communication having a low crosstalk level similarly to a conventionally known communication system using the CDMA system is implemented at a low cost.
According to a thirtieth aspect of the present invention, a communication method comprises the steps of: (a) preparing a user terminal comprising: a semiconductor element having a polycrystal; an encoder circuit converting an electric characteristic of said semiconductor element to a digital signal so that the value is dispersed in derivation from dispersion of the crystal structure of said polycrystal thereby generating and outputting a code; and a body part for transmitting and receiving a signal to and from a business connection, and transmitting said code to said business connection, (b) said user terminal transmitting said code said business connection; (c) said business connection recording said code; (d) said user terminal and said business connection making communication for electronic business transaction with each other.
Preferably, the communication method further comprises the steps of: (e) after said step (b) and before said step (d), said business connection determining by use of said code transmitted at said step (b) whether or not an access from said user terminal is illegal use by an unrightful user; and (f) said business connection stopping communication with said user terminal when said access is confirmed illegal at said step (e).
According to the thirtieth aspect, the code generated from the polycrystal is applied to an evidence seal in electronic business transaction, whereby a high barrier is implemented against illegal electronic business transaction by unrightful user terminal.
A thirty-first aspect of the present invention is directed to a semiconductor device. According to the thirty-second aspect, the semiconductor device comprises: a semiconductor substrate having a main surface and a polycrystalline region selectively formed in said main surface with remaining part thereof being single-crystalline; a first semiconductor circuit element having single-crystalline semiconductor portion selectively formed in said main surface other than said polycrystalline region; and a second semiconductor circuit element having polycrystalline semiconductor portion selectively formed in said polycrystalline region of said main surface.
According to the thirty-first aspect, both a semiconductor circuit element having single-crystalline semiconductor portion and a semiconductor circuit element having polycrystalline semiconductor portion are, as bulk type elements, integrated into a common semiconductor substrate.
A thirty-second aspect of the present invention is also directed to a semiconductor device. According to the thirty-third aspect, the semiconductor device comprises: a semiconductor substrate having a main surface; an insulator layer selectively formed on said main surface of said semiconductor substrate; a capacitor having: a first electrode formed of polycrystalline semiconductor and selectively formed on said insulator layer; an insulator film covering said first electrode; and a second electrode formed of polycrystalline semiconductor and facing said first electrode through said insulator film, a first MOS transistor having: a gate electrode formed of polycrystalline semiconductor and selectively formed on said insulator layer; a gate insulator film covering said gate electrode; and a polycrystalline semiconductor layer selectively formed over said insulator layer, said polycrystalline semiconductor layer including a channel region facing said gate electrode through said gate insulator film and source-drain regions interposing said channel region therebetween; and a second MOS transistor having: another gate insulator film selectively formed on said main surface of said semiconductor substrate; another gate electrode formed of polycrystalline semiconductor and formed on said another gate insulator film; another channel region selectively formed in said main surface of said semiconductor substrate facing said another gate electrode through said another gate insulator film; and another source-drain regions selectively formed in said main surface of said semiconductor substrate so as to interpose said another channel region therebetween.
According to the thirty-second aspect, three types of circuit elements integrated into a common semiconductor substrate have portions capable of being formed in the same manufacturing step; therefore, the semiconductor device can be manufactured through a small number of steps at a low cost.
An object of the present invention is to provide a semiconductor device capable of improving security against illegal use of a user terminal or the like without increasing the number of manufacturing steps and the manufacturing cost and a method of manufacturing the same. Another object of the present invention is to provide a communication method suitable for utilizing the semiconductor device.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.